1. Field of the Invention
The present invention relates to a RF coaxial connector.
2. Description of Related Art
RF coaxial connectors are used for providing interconnection between circuit boards, between RF modules, or between circuit boards and RF modules. In these applications, the allowable tolerance between relative positions of two connected elements tends to increase so as to facilitate fabrication of the elements and reduce the fabrication cost.
Currently, there are several circuit board interconnection techniques that allow axial and radial offsets between circuit boards. The oldest technique is based on standard snap-on connectors, such as SMB and MCX connectors, which have sockets and plugs for interconnecting the circuit boards. As shown in FIG. 1, in such a connector, inner conductors and outer conductors thereof have a staggered pin and insertion hole arrangement, which allows a limited axial offset. Since the elastic insertion holes of the inner and outer conductors only can tolerate extremely small axial and radial offsets, the number of the connectors disposed to a circuit board is not more than three pairs. In order to overcome the drawback, a second circuit board interconnection technique uses an adapter as an intermediate connection element, such as MMBX and SMP series on the market. The adapter can have a small rotation relative to a socket fixed to a circuit board, thereby allowing a radial offset of L sin(α). Therein, L is the length of the adapter and α is the rotational angle of the adapter. As shown in FIG. 2, the axial offset and the radial offset angle of a SMP connector with the maximum board-to-board distance H are ±0.3 mm and ±4°, respectively, and the axial offset and radial offset angle of a MMBX connector is ±0.70 mm and ±4.5°, respectively. The RF electrical performance of the above-described connectors depends on the degree of impedance match at the interconnection interface of the connectors. An air gap at the connection interface leads to high impedance of the region.
In addition, in order to ensure a sufficiently large offset angle in the case of a minimum tolerance along the axial distance H, the joining distance between the pins and insertion holes of the center conductors must be as small as possible such that over-stress does not occur when the center conductors have an angle offset, which however limits the increase of the axial offset of the connectors with the board-to-board distance H.